Crystal Structure of the RC-LH1 Core Complex from <i>Rhodopseudomonas palustris</i>

Abstract

The crystal structure at 4.8 angstrom resolution of the reaction center-light harvesting 1 (RC-LH1) core complex from Rhodopseudomonas palustris shows the reaction center surrounded by an oval LH1 complex that consists of 15 pairs of transmembrane helical alpha- and beta-apoproteins and their coordinated bacteriochlorophylls. Complete closure of the RC by the LH1 is prevented by a single transmembrane helix, out of register with the array of inner LH1 alpha-apoproteins. This break, located next to the binding site in the reaction center for the secondary electron acceptor ubiquinone (UQB), may provide a portal through which UQB can transfer electrons to cytochrome b/c1.